Issue 57: Seeking Saline Solutions

As governments and growers grapple with salinity problems, Western Australian grower ANN GRAHAM writes that the spreading salt scalds and dead trees are monuments to the sins of over-clearing, and that the idea of establishing a ‘set-and-forget’ system is proving elusive where ground water is the primary water source.

Like all prudent investors, we first checked the resources. The lab report was encouraging: the water from an ancient well would be ideal for hydroponics, and quantities were ample. Now, four years and more than $100,000 of infrastructure later, we are struggling with an unforeseen rising salt problem which is adding significantly to costs and time.

Burroloo Well Hydroponics before the addition of two new tunnels.

Our property at Upper Chittering in the Darling Range, 75km north of Perth, Australia, has long had an idiosyncratic water history. Most landholders rely on dams, rather than take financial risks probing the laterite hills for the elusive fresh and abundant aquifer. However, dams leak and the annual evaporation rate is three metres, so surface-stored water is never reliable.

We now have about 1400 square metres under plastic in six tunnels, using an NFT system to grow Daniela tomatoes and Cherisita cherry tomatoes. We also have 150 square metres under shade, experimenting with lettuce, silver beet, farm trees, herbs and other crops in double-deck PVC gullies.

Most produce is sold at the farm gate and to local retailers with favourable comments about taste being attributed to the salt content. But the well water, which now registers up to 1600ppm TDS in summer, is causing problems which offset the advantages of flavour. These include struggling to keep the nutrient mix EC level down, and more frequent dumping which adds to the overall water use. Salt deposits on plant leaves when using Netafim cooling foggers in the tunnels, has hampered growth.

Attempted solutions so far have included installing a Citor 5000 litre/day desalinator, though we are encountering yet-to-be resolved problems with the filters getting clogged by colloidal clay which did not show in lab tests. (The hypersaline run-off is pumped into a shallow pond for evaporating). We are also seeking surface run-off water from neighbours. While some have a surplus in winter, our needs are in summer.

The annual rainfall in Upper Chittering is around 650mm. We have five wet winter months with night temperatures sometimes dropping close to freezing. During the seven dry months, midsummer day temperatures can rise to the high 30’s and beyond.

” . . . there is no urgent remedial action by governments.”
Clearing of the jarrah trees and Wandoo Hills has long been restricted, but hydrogeologists tell us that the water we are using was probably laid down decades ago when the bulldozers rumbled across the landscape. This may explain why we are still getting TDS readings of above 1000ppm when the well overflows in winter.

Unlike the Western Australian wheatbelt, where spreading salt scalds and groves of dead trees in a funereal ghostscape are monuments to the sins of over-clearing, Upper Chittering retains much timber and shows no obvious signs of distress. Consequently, there is no urgent remedial action by governments.

In winter the hills stay green and lovely, and the creeks splash through reedbeds into lakes fringed with paper-barks. It needs a TDS metre and longitudinal readings to check the reality, along with knowledge that catfish have now disappeared from the Brockman River and nutrient levels from top-dressing have stopped citrus growers irrigating their orchards.

Concerns about poisoning the landscape and overstocking our 280-hectare property, where a breeding flock of 800 crossbred ewes was never sufficient to maintain an income from prime lamb and wool, pushed us towards hydroponics. We had seen scores of projects in New Zealand where growers, generous with their time, impressed us with a philosophy of sustainable agriculture, through land conservation and frugal water use.

Encouraged by Carl Barry at Growth Technology in Fremantle, who supplies nutrient mixes and on-the-spot advice, we are still pursuing a solution to the salt problem. Agriculture WA tends to concentrate on broadacre farming issues and has been of little assistance.

“We are planting hundreds of trees every year in a bid to push the salt back underground”

Ann Graham tending new plants. Note the overhead misting system.

Rainfall is collected from shed roofs, but so far we have been unable to determine how to harvest water from the curved plastic tunnels. We create a cocktail with the well water, rainwater and desalinated water, and pump to five tanks each holding 90,000 litres. We will probably have to increase our total storage capacity to 750,000 litres to ensure that we can survive a long summer.

Trying to get a good balance with an acceptable TDS of around 700-800ppm requires much daily adjustment of tanks and pumps. The idea of establishing a set-and-forget system is proving elusive, and our budget has blown out by at least 50 percent.

We employ part-time staff for pruning, picking and other regular tasks, but do the tricky water-balancing ourselves. This is onerous because we both have other work off-farm.

We are also planting hundreds of trees every year in a bid to push the salt back underground, but not all our catchment neighbours are enthusiastic. As Perth expands the demand for small holdings has encouraged developers to buy large holdings and subdivide. Although many genuine urban escapees are keen arborealists, the speculators are reluctant to open wallets.

We face all the usual pest and disease hassles which go with hydroponics, while recognising that good management is the most important factor in making our venture a commercial success. We are trying to make the operation chemical pesticide free, so we are returning to traditional sulphur sprays where possible.

“Salt is an issue which has to be faced.”

Granddaughter Kate Graham helping to sort the tomato crop.

The cost of desalinating and pumping has yet to be evaluated. Pumps have to run 24-hours a day to keep up with demand, so our hopes of using time switches to restrict usage to low-tariff periods, have been frustrated.

Tomatoes are the most salt-tolerant of vegetables, but growth rates are slowed once the TDS exceeds 1000ppm, and fruit size also appears to be affected. We are seeking other produce which can cope with our water, and which is saleable and profitable.

The salt problem was never anticipated, and coping with this is taking time which should be used for crop care and the quiet observations so necessary to spot the pests before they exploit our distractions.

Salt is an issue which has to be faced. The clearing sins of our fathers are being visited on their children of today. This generation has the task of finding solutions, and hydroponics could help find answers.

On one hectare of our property, which previously yielded a bale of hay, a fleece and maybe a lamb or two every year, we are growing up to 5000 plants and developing a body of knowledge which may come in use for others confronting the spectre of salt. In any case, we’ve invested too much in time and dollars to give up now.